Geographic characterization of intra-articular pathologies in early-stage avascular necrosis of the hip.

BACKGROUND: Avascular necrosis (AVN) of the hip is a progressive condition that often leads to femoral head collapse, necessitating total hip arthroplasty. While core decompression (CD) is commonly performed for the treatment of early-stage AVN, the incidence and geographic location of concomitant intra-articular pathologies that may contribute to symptoms and disease progression are incompletely understood. HYPOTHESIS / PURPOSE: The purpose of this study was to describe the prevalence, anatomical distribution, and diagnostic concordance of MRI vs. arthroscopy in detecting intra-articular pathology in early-stage AVN. We hypothesized that early-stage hip AVN would be associated with a high prevalence of intra-articular pathology in specific anatomic zones, and that higher Ficat stage would be associated with a greater frequency of these lesions. METHODS: Patients who underwent arthroscopic-assisted core decompression (CD) by two surgeons for symptomatic early-stage AVN between March 2020 and December 2024 were retrospectively identified. Preoperative radiographs and MRIs were reviewed by a fellowship-trained musculoskeletal radiologist to characterize AVN involvement of the femoral head, labral tears, chondral pathologies, and synovitis/effusion, using the geographic zone method. MRI interpretations were compared to intraoperative arthroscopic findings. Associations between the Ficat stage and the prevalence of intra-articular pathologies were assessed. RESULTS: A total of 36 hips in 30 patients were analyzed. Among all hips analyzed, three (8.3%) were Ficat stage 1, 25 (69.4%) were Ficat stage 2a, and eight (22.2%) were Ficat stage 2b. AVN most affected zones 2 and 3 of the femoral head, which frequently corresponded to the locations of labral tears and acetabular transition zone chondral lesions. A high prevalence of labral tears (88.9%), acetabular cartilage lesions (75%), and synovitis (61.1%) was observed. MRI interpretations almost always correlated with arthroscopic findings, although arthroscopy was more sensitive in detecting grade 1 softening of the femoral head and acetabular cartilage. Higher Ficat stage was associated with a higher prevalence of labral tears (p=0.02), acetabular cartilage lesions (p<0.01), femoral head cartilage lesions (p<0.01), and synovitis/effusion (p=0.02). CONCLUSIONS : Early-stage hip AVN is associated with a high prevalence of intra-articular pathologies, with increasing Ficat stage correlating with more frequent labral tears, transition zone and femoral head cartilage lesions, and synovitis/effusion. While MRI accurately identified and localized most intra-articular pathologies, arthroscopy was more sensitive for detecting grade 1 cartilage lesions. CLINICAL RELEVANCE: Arthroscopic-assisted core decompression offers an opportunity to identify and treat intra-articular pathology that may contribute to pain and disease progression in early-stage hip AVN. Recognizing the high prevalence and location of these lesions may help optimize surgical decision-making and long-term outcomes. STUDY DESIGN: Retrospective case series; Level of evidence, 4.